Unresponsiveness to meglumine antimoniate in anthroponotic cutaneous leishmaniasis field isolates: analysis of resistance biomarkers by gene expression profiling

Abstract

Background: Resistance to antimonials is a fundamental determinant of treatment failure in anthroponotic cutaneous leishmaniasis (ACL). Detection of reliable molecular markers to distinguish unresponsive and responsive parasites is critical for consolidating strategies to monitor drug efficacy.

Methods: We analysed the expression of five major antimony resistance-associated genes that is aquaglyceroporin1 (AQP1), γ-glutamylcysteine synthetase (γ-GCS), multidrug resistance protein A (MRPA), trypanothione reductase (TR) and thiol-dependent reductase 1 (TDR1), in unresponsive and responsive Leishmania tropica field isolates by quantitative real-time PCR in comparison with sensitive and resistant reference strains.

Results: Gene expression analysis showed the down-regulation of AQP1, γ-GCS and TDR1 by a factor of 1.9, 1.7 and 3.55, respectively, in unresponsive isolates vs. responsive ones. The average RNA expression level of MRPA increased by a factor of 1.9 in the unresponsive group. Isolates exhibited a strong positive linear correlation between gene expression of AQP1 and γ-GCS. A negative correlation between the AQP1 and γ-GCS expression level and lesion duration in responsive patients indicated the potential role in diagnosing drug-unresponsive parasites in endemic areas of ACL.

Conclusion: In cases of inconclusive outcomes of resistance tests in clinical isolates, expression analysis of a set of influential genes can be beneficial to identify distinctive biomarkers between antimony-unresponsive and responsive parasites.

Keywords: Leishmania tropica; Iran; Leishmania tropica; antimonial resistance; genetic markers; marqueurs génétiques; qPCR en temps réel; real-time qPCR; résistance antimoniale.